| Although unconformity-type uranium deposits have been exploited for 30 years their formation remains problematic. This study represents an investigation of the controls of mineralization at Key Lake, one of Saskatchewan's largest unconformity-type uranium deposits. An integrated approach was employed to determine the roles of lithology, structure, paleotopography, and alteration in the mineralization process. This approach involved detailed mapping of rocks hosting the Deilmann orebody (Deilmann pit), and related structural analysis, depth to basement mapping, study of clay mineral alteration, and petrography.; Documentation of the relative age of structures has led to the recognition of six phases of deformation. The first four were Paleoproterozoic, ductile to brittle-ductile events related to Trans Hudsonian orogenesis. The last two were brittle events that occurred after deposition of the late Paleoproterozoic - early Mesoproterozoic Athabasca Group. Mineralization is interpreted to have been controlled by post-Athabasca brittle faults which largely represent reactivation of older, more ductile Trans-Hudsonian structures. The latter, in turn, are localized in the weakest, graphitic rocks of the basement. The Key Lake fault, which exhibits up to 12 m of reverse offset, represents the most significant post-Athabasca structure. (Abstract shortened by UMI.)... |
